Apparatus and method for doping

ABSTRACT

There is proposed an apparatus for doping a material to be doped by generating plasma (ions) and accelerating it by a high voltage to form an ion current is proposed, which is particularly suitable for processing a substrate having a large area. The ion current is formed to have a linear sectional configuration, and doping is performed by moving a material to be doped in a direction substantially perpendicular to the longitudinal direction of a section of the ion current.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a doping apparatus and a method ofdoping used for the manufacture of semiconductor integrated circuits andthe like. More particularly, the present invention relates to an iondoping apparatus and a method of doping having a configurationpreferable for processing substrates having large areas, wherein ionbeams are radiated to a semiconductor material composed of amorphouscomponents partly or entirely or to a substantially intrinsicpolycrystalline semiconductor material to supply impurities to thesemiconductor material.

2. Description of Related Art

Methods of forming p-type and n-type impurity regions in a semiconductorduring the manufacture of semiconductor integrated circuits and the likeare known in which ions of impurities that produce n and p conductivitytypes (n-type impurities and p-type impurities) are radiated andimplanted by accelerating them by a high voltage. Especially, a methodof separating mass and charge ratio of ions is referred to as “ionimplantation” and are widely used for the manufacture of semiconductorintegrated circuits.

Another method is known in which plasma including n-type and p-typeimpurities is produced and ions in the plasma are accelerated by a highvoltage to be implanted in a semiconductor as an ion current. Thismethod is referred to as “ion doping” or “plasma doping”.

The structure of a doping apparatus utilizing ion doping is simpler thanthat of a doping apparatus utilizing ion implantation. For example, toimplant boron as p-type impurities, plasma is produced in a gas ofdiborane (B₂H₆) which is a boron compound by means of RF discharge orthe like and a high voltage is applied to the plasma thereto to extractions including boron which are in turn radiated into a semiconductor.Since gas-phase discharge is performed to produce plasma, the degree ofvacuum inside the doping apparatus is relatively high.

Presently, an ion doping apparatus is frequently used to add impuritiesuniformly to a substrate having a relatively large area. This is becausean ion beam to cover a large area can be relatively easily obtained inan ion doping apparatus which does not perform separation on a massbasis. On the other hand, for an ion implantation apparatus which mustperform separation on a mass basis, it is difficult to increase the areaof a beam while maintaining the uniformity of the ion. Therefore, an ionimplantation apparatus is unsuitable for a substrate having a largearea.

Recently, studies are active on the reduction of the temperature forsemiconductor device processing. This is largely because of the factthat a necessity has arisen to form semiconductor devices on inexpensiveinsulated substrates made of glass and the like. Other reasons includeneeds associated with the trend toward microscopic devices andmulti-layer devices.

Insulated substrates made of glass or the like have various advantagescompared to silica substrates which have been used in processing at hightemperatures in that they are easy to process, easy to form with a largesurface area, inexpensive, and so on. However, as a matter of fact, thetrend toward substrates having larger areas has also resulted in variousdifficulties to be technically overcome including a need for developingapparatuses having characteristics different from those suitable forconventional processes at high temperatures.

Ion implantation is disadvantageous for the manufacture of active matrixtype liquid crystal displays and like wherein substrates having a largearea must be processed, and ion doping is under research and developmentin an intention to cover such a disadvantage.

FIGS. 1 and 2 schematically illustrate a conventional ion dopingapparatus. FIG. 1 schematically illustrates an ion source and an ionaccelerator mainly. FIG. 2 illustrates the structure of the ion dopingapparatus as a whole. The description will first proceed with referenceto FIG. 1. Ions are generated in a plasma space 4.

Specifically, radio-frequency power is applied between an electrode 3and a mesh electrode 6 by a radio-frequency power supply 1 and amatching box 2 to generate plasma in the plasma space 4 under a reducedpressure. Hydrogen or the like is introduced at the initial stage ofplasma generation, and diborane and phosphine (PH₃) which are dopinggases are introduced after the plasma is stabilized.

The electrode 3 and the outer wall of the chamber (at the same potentialas that of the mesh electrode 6) are insulated from each other by aninsulator 5. An ion current is extracted from the plasma thus generatedby an extraction electrode 10 and an extraction power supply 8. The ioncurrent thus extracted is shaped by a suppressor grid 11 and asuppressor power supply 9 and thereafter accelerated into requiredenergy by an acceleration electrode 12 and an acceleration power supply7.

FIG. 2(A) will now be described. The ion doping apparatus is generallycomprised of an ion source/accelerator 13, a doping chamber 15, a powersupply device 14, a gas box 19, and an exhaust device 20. In FIG. 2, theion source/accelerator as in FIG. 1 arranged horizontally. That is, inFIG. 2, the ion current flows to the right (downward in FIG. 1). Thepower supply device 14 mainly consists of power supplies used forgeneration and acceleration of ions and includes the radio-frequencypower supply 1, matching box 2, acceleration power supply 7, extractionpower supply 8, and suppressor power supply 9.

A substrate holder 17 is provided in the doping chamber 15, and amaterial 16 to be doped is placed thereon. In general, the substrateholder is designed such that it can be rotated about an axis in parallelwith the ion current. The air in the ion source/accelerator 13 and thedoping chamber 15 is exhausted by the exhaust device 20. The air in theion source/accelerator 13 and the doping chamber 15 may be exhausted byseparate exhaust devices.

A doping gas is delivered from the gas box 19 to the doping chamber 15through a gas line 18. While a gas intake port is provided between theion source/accelerator 13 and the material 16 to be doped in theapparatus shown in FIG. 2(A), it may be provided in the vicinity of theplasma space 4 of the ion source. The doping gas is generally used bydiluting it with hydrogen or the like.

In the conventional ion doping apparatus, the area of a substrate(material to be doped) has been equal to or smaller than the sectionalarea of the plasma space 4 in the ion source 13. This is a requirementto be satisfied to achieve uniform doping. FIG. 2(B) illustrates asection which is perpendicular to the ion current. Specifically, the ionsource/accelerator 13 has a size represented by L₁ and L₂, and thedoping chamber 15 and a material 17 to be doped are sized such that theycan be contained therein. The dimensions L₁ and L₂ are about the same.

Therefore, the size of the plasma space 4 must be increased with thesize of the substrate. Further, plasma must have two-dimensionaluniformity. However, it is difficult to increase the size of the plasmaspace infinitely. The reason is that this makes the generation of plasmanonuniform. This is primarily attributable to the fact that the meanfree path of molecules becomes sufficiently smaller than the section ofthe plasma space. It is therefore difficult to make the length of oneside of the plasma space equal to or greater than 0.6 m.

SUMMARY OF THE INVENTION

The present invention is characterized in that an ion current is shapedto have a linear or rectangular section and in that a material to bedoped is moved perpendicularly to the longitudinal direction of the ioncurrent (i.e., in the direction of the shorter dimension of the ioncurrent). As a result, plasma is required to be uniform only in thelongitudinal direction, and this makes it possible to process asubstrate having a large area. What is to be considered is only theuniformity of plasma in the longitudinal direction and nottwo-dimensional uniformity because irradiation with ions is carried outby scanning in any part of the material to be doped.

According to the present invention, in principle, while the length ofone side of a substrate is limited by the length of plasma, there is nofactor limiting the length of another side of the substrate other thanthe size of the doping chamber. It is easy to generate plasma whoseuniformity is maintained for about two meters in the longitudinaldirection thereof if the width of the discharge space is sufficientlysmall. It goes without saying that the width of the ion beam is on theorder of centimeters.

Therefore, such a linear ion doping apparatus is suitable for processinga substrate having a large area and processing a multiplicity ofsubstrates simultaneously. For example, it can relatively easily dopesubstrates of sizes up to 2 m×x m where x is determined by the size ofthe doping apparatus.

FIG. 3(A) illustrates the conception of the present invention. An iondoping apparatus according to the present invention comprises an ionsource/accelerator 13, a doping chamber 15, a power supply device 14, agas box 19, and an exhaust device 20 as in the prior art. Unlike theprior art, however, the ion source/accelerator 13 generates an ioncurrent having a linear or rectangular section. Further, a substrateholder 17 includes a mechanism which moves during doping. Thelongitudinal direction of the ion current is a direction perpendicularto the plane of the drawing.

In the ion doping apparatus according to the present invention, theshape of a substrate (material to be doped) that can be processed has norelationship with the sectional shape of a plasma space 4 in the ionsource 13. However, the length of one of the shorter sides of thesubstrates must be equal to or less than the length of the plasma space4 in the longitudinal direction thereof. There is no factor that limitsthe size of another side of the substrate other than the size of thedoping chamber.

FIG. 3(B) illustrates a section perpendicular to the ion current.

Specifically, the shape of the ion source/accelerator 13 (L₁×L₂) is notlimited by the shapes of the doping chamber 15 and a material 17 to bedoped. Since the ion current has a linear or rectangular sectionalshape, L₁<L₂ (=the longer dimension of the section of the ion current).

The statement that an ion current is required to be uniform only in thedirection of the longer dimension and not in the direction of theshorter dimension thereof implies that no problem arises even if thereis distribution of ionic strength and ionic species in the direction ofthe shorter dimension of the ion current. This is advantageous inremoving certain light ions (e.g., H+ and H₂+) from the ion current. Ithas been necessary to exert a magnetic action on an ion current toseparate ions therein, which has inevitably affected the distribution ofheavy ions which have been required.

With conventional ion doping apparatuses in which two-dimensionaluniformity has been required, it is substantially impossible to separateions. According to the present invention, however, it is easy to performseparation as shown in a second embodiment thereof.

The fact that an ion current is required to be uniform only in thedirection of the longer dimension and not in the direction of theshorter dimension thereof is advantageous from the viewpoint of thestructure of an electrode for accelerating and decelerating the ioncurrent. A mesh-like or porous electrode has been frequently used inconventional ion doping apparatuses. However, in the case of such anelectrode, since a part of ions collide with the main body of theelectrode, deterioration of the electrode or splashing and sputtering ofsubstances that form the electrode can be a problem.

On the contrary, according to the present invention, the above-describedproblem is solved because an electrode having a simple configuration isprovided in a position apart from an ion current as shown in a firstembodiment.

Known conventional semiconductor manufacturing techniques include ionimplantation which involves a known technique for scanning an ioncurrent across a fixed substrate by electromagnetically deflecting thesame. However, such a method is unsuitable for doping ions havingvarious mass-to-charge ratios as in the present invention, and it ispreferable to move the substrate with the ion current fixed as carriedout according to the present invention.

The reason is that, according to the technique for electromagneticallydeflecting an ion current, light ions are much easily deflected thanheavy ions and therefore can not be scanned uniformly. Since adifference of only one in mass numbers can cause distribution, it is notpreferable to apply this technique to ion doping techniques to which thepresent invention is directed. The use of such a technique forelectromagnetic deflection is limited to doping of only one ion species.

An ion doping apparatus according to the present invention may be addedwith an ion focusing apparatus and an ion mass separating apparatuswhich are well known in the prior ion-related art.

In a linear ion doping technique like the present invention, the featureof easy ion mass separation can result in an advantage also in asubsequent annealing process. In general, when ion doping is performed,the incidence of ions upon the substance being irradiated can result indamage to a lattice of atoms of the substance under irradiation,transition of a lattice into an amorphous state, and the like. Further,it is not possible to cause the dopant to work as a carrier by simplyimplanting it in a semiconductor material. Several steps are required tofollow doping in order to solve these problems.

The most popular method employed in such steps is thermal annealing oroptical annealing. Dopant can be combined with a lattice of asemiconductor material by performing such annealing. In the case ofoptical annealing, however, light must reach a location where damage toa lattice has occurred or the like as described above.

It is considerably common to perform another step of adding hydrogen toeliminate levels (uncombine arms) which have survived theabove-described annealing. Such a step is referred to as“hydrogenation”. Hydrogen easily enters in a semiconductor material at atemperature on the order of 350° C. and eliminates the levels asdescribed above.

In any case, the inclusion of such steps after doping is not preferablefrom the viewpoint of cost and throughput because it increases thenumber of steps. By performing thermal annealing and hydrogenationsimultaneously with doping or performing a part of those steps duringdoping, it is possible to eliminate separate steps for annealing andhydrogenation, to reduce processing time or to decrease the processingtemperature.

It is relatively easy to add hydrogen and dopant in a semiconductormaterial simultaneously. Specifically, doping may be performed bydiluting dopant with hydrogen and ionizing it together with hydrogen.For example, if ion implantation is carried out by the doping apparatusas shown in FIGS. 1 and 2 using phosphine (PH₃) diluted with hydrogen,hydrogen ions (e.g., H₂+ and H+) will be implanted along with ionsincluding phosphorus (e.g., PH₃+ and PH₂+).

However, since hydrogen is too light and easily accelerated compared toions including dopant such as phosphorus and boron, it penetrates toodeep in the substrate. On the other hand, ions including dopant stay ina relatively shallow region. Therefore, in order for hydrogen to correctdefects caused by dopant, hydrogen must be moved by means of thermalannealing or the like.

Meanwhile, the use of a linear ion beam makes it possible to irradiate asubstrate with only desired ions by providing a mass separator on theway of an ion current as described above. A new doping method asdescribed below can be derived from such an idea. That is a dopingmethod wherein ions having different mass are separated and thenaccelerated at different voltages, and resultant beams are radiated to asemiconductor material to implant those ions to substantially the samedepth.

For example, separation is performed to obtain ions mainly composed ofhydrogen (light ions) and ions including dopant (heavy ions), and onlythe latter is accelerated to make the depths of penetration of the lightand heavy ions substantially the same. Thus, the presence of the lightions makes it possible to simultaneously perform a part of or all of anannealing step and a hydrogenation step on the dopant.

Specifically, the speed of incidence of a hydrogen ion beam upon asemiconductor material is made close to the speed of incidence of an ionbeam containing the dopant upon the semiconductor material. As a result,the distribution of hydrogen in the semiconductor film is made close tothe distribution of the dopant. At this time, the dopant is immediatelyactivated by incidence energy of ions (which is converted into thermalenergy as a result of collision) and the presence of hydrogen. Thiseffect allows a subsequent dopant activation step to be eliminated.

The depth of penetration of each ion beam may be adjusted by changingits angle of incidence. The smaller the angle of incidence, the smallerthe depth of penetration. The angle of incidence may be changed bymagnetic and electrical effects. Ions can not enter a substrate and arereflected therefrom if the angle of incidence is too small. An angle ofincidence of 40° or more will be sufficient.

For the above-described purpose, a mass separator may be providedbetween an ion beam generator and an accelerator. Further, massseparation can be performed on an ion beam using an apparatus whichapplies a magnetic field in parallel with the longitudinal direction ofthe ion beam.

Ion implantation into a semiconductor material may be carried out byimplanting ions including dopants first and implanting ions mainlycomposed of hydrogen thereafter or may be performed in the reversedorder.

It will be advantageous to provide an ion doping apparatus and a laserannealing apparatus utilizing a linear laser beam according to thepresent invention in the same chamber. Specifically, it is much moreadvantageous to combining them into a single apparatus than providingthem as separate apparatuses considering the fact that the presentinvention is characterized by a step of doping a substrate whilescanning it with a linear ion current; a laser annealing processutilizing a linear laser beam according to another aspect of theinvention needs a similar mechanism to be implemented; and stepsutilizing those apparatuses are performed consecutively.

For example, Japanese unexamined patent publication (KOKAI) No.H7-283151 discloses a multi-chamber vacuum processing apparatusincluding an ion doping chamber and a laser annealing chamber. The ideaof integrating an ion doping chamber and a laser annealing chamber hasnot been adopted in conventional ion doping apparatuses which have beenbased on irradiation using an ion current having a planar section at atime and which have sometimes required a substrate to be rotated.

However, according to the present invention wherein an ion dopingapparatus performs doping while moving a substrate with a transportmechanism similar to that of a linear laser annealing apparatus, thereis no need for providing an ion doping chamber and a laser annealingchamber separately, and it is rather advantageous to integrate them fromthe viewpoint of productivity on a mass production basis. Specifically,an arrangement may be made wherein the longitudinal direction of asection of an ion current is in parallel with the longitudinal directionof a section of a laser beam and wherein a substrate is moved betweenthem perpendicularly to the above-mentioned directions. This makes itpossible to perform an ion doping step and a laser annealing stepconsecutively.

The combination of a linear ion processing apparatus with a linear laserannealing apparatus has an advantage, in addition to the advantage ofreducing the number of steps by performing the two steps simultaneously,in that the possibility of contamination of a substrate is reduced.

Further, the use of an ion doping apparatus according to the presentinvention allows a doping process having features as described below. Afirst method of doping according to the present invention comprises thesteps of generating a linear ion beam, separating the ion beam into atleast two ion beams through mass separation on the ion beam,accelerating the ion beams by different voltages, and radiating the ionbeams to a substrate at different angles.

A second method of doping according to the present invention ischaracterized in that it comprises the steps of generating a linear ionbeam, performing mass separation on the ion beam to obtain at least twokinds of ion beams, accelerating one of the ion beams by an accelerationvoltage different from that for the other, and radiating the at leasttwo ion beams to a substrate while moving the substrate in a directionsubstantially perpendicular to the linear direction of the linearlyprocessed ion beams.

A third method of doping according to the present invention ischaracterized in that it comprises the steps of generating a linear ionbeam including hydrogen, separating the ion beam on a mass basis into anion beam mainly composed of hydrogen and another ion beam, applyingenergy and incident angles to the ion beam mainly composed of hydrogenand the other such that the depths of penetration of those ion beamsinto a substrate substantially equal each other, and radiating the ionbeams to the substrate while moving the substrate in a directionsubstantially perpendicular to the linear direction of the linearlyprocessed ion beams.

A more detailed description of the present invention will be made laterwith reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 schematically illustrates an ion source/accelerator of aconventional ion doping apparatus.

FIGS. 2(A) and 2(B) schematically illustrate a configuration of aconventional ion doping apparatus.

FIGS. 3(A) and 3(B) schematically illustrate a configuration of an iondoping apparatus according to the present invention.

FIG. 4(A) schematically illustrates an ion source/accelerator of an iondoping apparatus according to a first embodiment of the presentinvention.

FIG. 4(B) schematically illustrates a configuration of electrodes of thefirst embodiment.

FIG. 5(A) schematically illustrates an ion source/accelerator of an iondoping apparatus according to a second embodiment of the presentinvention.

FIGS. 5(B) and 5(C) illustrate principles of operation of the secondembodiment.

FIG. 6(A) schematically illustrates an ion source/accelerator of an iondoping apparatus according to a third embodiment of the presentinvention.

FIGS. 6(B), 6(C), 6(D), and 6(E) illustrate principles of operation ofthe third embodiment.

FIGS. 7(A) and 7(B) schematically illustrate a configuration of an iondoping apparatus according to a fourth embodiment of the presentinvention.

FIG. 8 schematically illustrates an ion source/accelerator of ion dopingapparatuses according to fifth and sixth embodiments of the presentinvention.

FIG. 9 schematically illustrates an ion source/accelerator of ion dopingapparatus according to a seventh embodiment of the present invention.

FIGS. 10(A), 10(B), 10(C), and 10(D) are views showing the relationshipbetween the speed of incidence of ions and the depth of penetration ofthe same.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS First Embodiment

A first embodiment of the present invention will now be described. FIGS.4(A) and 4(B) illustrate the present embodiment. FIG. 4(A) schematicallyillustrates an ion source/accelerator of an ion doping apparatusaccording to the present embodiment, and 4(B) schematically illustratesa configuration of electrodes of the ion source/accelerator of thepresent embodiment. The description will first proceed with reference toFIG. 4(A).

In a plasma space 24 having a rectangular section, a radio-frequencypower is applied between plasma generation electrodes 23 and 26 by aradio-frequency power supply 21 to generate plasma. This plasma isextracted by an extraction electrode 30 and an extraction power supply28, conditioned by a suppressor electrode 31 and a suppressor powersupply 29 in terms of the shape and distribution thereof, and thereafteraccelerated by an acceleration electrode 32 and an acceleration powersupply 27 into required energy. If the plasma is sufficiently uniform inthe longitudinal direction thereof, it is not necessary to provide thesuppressor electrode 31.

FIG. 4(B) illustrates a configuration of the plasma generationelectrodes 23 and 26, the extraction electrode 30, the suppressorelectrode 31, and the acceleration electrode 32. Specifically, theextraction electrode 30, the suppressor electrode 31, and theacceleration electrode 32 have a cavity through which an ion currentflows at the center thereof. Therefore, no ion collides with theelectrodes.

In the present embodiment, the plasma generation electrodes 23 and 26may be spaced from each other by 1 to 10 cm and may have a length of 50to 150 cm; the shorter dimension of sections of the cavities in theextraction electrode 30, the suppressor electrode 31, and theacceleration electrode 32 may be 1 to 15 cm; and the longer dimensionthereof may be 50 to 170 cm.

This ion doping apparatus may have a general configuration similar tothat shown in FIGS. 3(A) and 3(B).

According to the present embodiment, ions are introduced without beingsubjected to mass separation. Therefore, when phosphine diluted withhydrogen is used as a doping gas for example, both of heavy ions (PH₃+,PH₂+ etc.) and light ions (H+, H₂+ etc.) are introduced with the sameareal density. The same thing occurs when boron or antimony isimplanted.

This is advantageous in that recrystallization occurs at a lowtemperature. Specifically, Si—H combinations in the material aresubjected to a condensation process in which hydrogen molecules aredesorbed to form Si—Si combinations. This differentiates the presentembodiments from second and third embodiments in which implantation ofhydrogen molecules is actively prevented.

It should be noted that the depth of penetration varies depending on themass and radius of ions in the present embodiment. In general, lighthydrogen-type ions concentrate in a much deeper region. Embodiments forcorrecting this will be described later (fifth, sixth, and seventhembodiments).

Second Embodiment

A second embodiment of the present invention will now be described. Thepresent embodiment shows an example in which a mass separator isprovided in the ion source/ion accelerator in the ion doping apparatusshown in the first embodiment. The present embodiment will be describedwith reference to FIGS. 5(A), 5(B), and 5(C). FIG. 5(A) schematicallyillustrates a configuration of an ion source/accelerator according tothe present embodiment. The description will now first proceed withreference to FIG. 5(A). In the plasma space 24, radio-frequency power isapplied to the plasma generation electrodes 23 and 26 by theradio-frequency power supply 21 to generate plasma.

This plasma is extracted by the extraction electrode 30 and theextraction power supply 28 and is accelerated by the acceleration powersupply 27. Then, it passes through magnetic fields 34 and 35 in oppositedirections and a slit 36 provided therebetween. The ions are subjectedto a lateral force in the magnetic field 34. As a result, light ions(e.g., H+ and H₂+ indicated by the dotted line in FIG. 5(A)) aredeflected more to the left than heavy ions (e.g., BH₃+, BH₂+, PH₃+, andPH₂+ which are indicated by the thin line in FIG. 5(A)) and thereforecan not pass through the slit 36. That is, the slit 36 is provided forseparation on a mass basis.

FIG. 5(B) is a conceptual illustration of the distribution of the ionsbefore they enter the slit. The ordinate represents the density of theions (ionic strength), and the abscissa represents the direction of theshorter dimension of a section of the ion current. The ions reflect thedistribution of the plasma and have a shape that resembles Gaussiandistribution. Light ions is moved to the left by the magnetic field 34.FIG. 5(C) shows the distribution of the ions after they pass through theslit. The slit 36 eliminates the peak of the light ions located leftwardfrom the ion current. Thus, separation on a mass basis can be carriedout on the ion current.

Even after passing through the slit 36, the distribution of the ioncurrent is still under strong influence of the magnetic field 34 in thedirection of the shorter dimension thereof and is different from that inthe plasma space. However, this results in no problem because doping isperformed by moving the ion current as described above.

After passing through the slit 36, the ion current is subjected to arightward force in the magnetic field 35 which is in the directionopposite to the magnetic field 34 to correct the path thereof. Since theforces applied to the ions in the magnetic fields 34 and 35 haveopposite directions and the same magnitude, the ion current finallybecomes in parallel with the initial flow.

Thereafter, the ions are conditioned by the suppressor electrode 31 andthe suppressor power supply 29 in terms of its shape and distributionand then accelerated by the acceleration electrode 32 and anacceleration power supply 33 into required energy. It is not necessaryto provide the suppressor electrode 31 if the plasma is sufficientlyuniform in the longitudinal direction thereof. The apparatus and slitfor applying magnetic fields as in the present embodiment may be locatedbetween the suppressor electrode and the acceleration electrode orbetween the acceleration electrode and a material to be doped.

When light hydrogen-type ions are to be removed as in the presentembodiment, the condensation reaction for desorbing hydrogen duringrecrystallization as described with reference to the first embodiment isnot likely to occur. In order to solve this problem, doping of onlyhydrogen may be performed before or after a step of doping impurities ofinterest to a similar depth.

Third Embodiment

A third embodiment of the present invention will now be described. Thepresent embodiment shows an example wherein an ion focusing device isprovided in an ion source/ion accelerator of an ion doping apparatusincluding a simple mass separator. The present embodiment will bedescribed with reference to FIGS. 6(A) through 6(E). FIG. 6(A)schematically illustrates a configuration of the ion source/acceleratorof the present embodiment. The description will first proceed withreference to FIGS. 6(A) and 6(B). FIG. 6(A) is a view of an ion currenttaken in the longitudinal direction of a section thereof, and FIG. 6(B)is a view of the ion current taken from a plane perpendicular to thelongitudinal direction of the section.

The ion source of the present embodiment employs a plasma generationmethod of induced excitation type unlike the first and secondembodiments. For this purpose, a silica tube is used in a part of a gasline 58, and an induction coil 43 is wound around it. The coil 43 isconnected to a radio-frequency power supply 41. One end of the coil isgrounded. A downstream current of the ion current is grounded in thefirst and second embodiments. On the contrary, an upstream current ofthe ion current is grounded in the present embodiment.

The advantage of this arrangement is that the gas line can be usedaround the level of the ground especially in cases such as inducedexcitation in a thin tube. When the gas line is provided in the middleof an ion current as in the first and second embodiments, the potentialof the gas line is not so critical. However, if a downstream current ofions is grounded in an apparatus as in the present embodiment, thepotential around the gas line can reach a voltage as high as 100 kV.Since conductive materials are used for the gas piping and gas bomb, itis necessary to extend strict insulation up to the gas box and the like.

When an upstream current of ions is grounded as in the presentembodiment, a downstream current will conversely have a (negative) highpotential. However, since only a few materials located downstream are incommunication with the outside, insulation is not critical for suchmaterials.

The plasma generated by the induction coil 43 is introduced in anacceleration chamber 44. The intake port to the acceleration chamber hasa unique configuration as shown in FIG. 6(B). At this time, since gasesare introduced from the thin tube into a reaction chamber having a largecapacity, the pressure and density of the plasma and doping gasesdecrease rapidly.

This is preferable when an ion current is to be focused as in thepresent embodiment. In general, the pressure in the gas line 58 at thearea of the induction coil may be ⅕ to 1/100 of the pressure in theacceleration chamber 44. A pressure of 10⁻⁴ Torr or more is required togenerate plasma.

However, the mean free path of molecules or ions of a gas becomes smallin a space under a high pressure, and this is disadvantageous inaccelerating ions into high energy. Further, when an ion current is tobe focused as in the present embodiment, scattering caused by ioncollision reduces the level of focusing.

The above-described problem can be solved by making the pressure in theacceleration chamber 44 significantly lower than that in the plasmasource (in the vicinity of the induction coil 43). In order to enhancethe focusing of an ion current, a pressure is preferably provided suchthat the distance between the focusing device and a material to be dopedis equal to or less than the mean free path.

The plasma introduced into the acceleration chamber as described aboveis extracted by the extraction electrode 50 (and the extraction powersupply 48) and is accelerated by the acceleration electrode 52 (and theacceleration power supply 47). A coil 51 for focusing an ion current isprovided between the extraction electrode 50 and the accelerationelectrode 52. The coil 51 has a configuration different from that of anormal solenoid.

Specifically, the diameter of the coil is gradually reduced as itextends downstream in the focusing direction of an ion current. On theother hand, the diameter is kept unchanged in the directionperpendicular thereto. This allows the ion current to be focused in onedirection. The coil 51 may be replaced with a hollow permanent magnethaving a similar configuration.

What described above is a method of confining or focusing plasmareferred to as “z pinch method” in principle. Alternatively, it ispossible to employ a self-focusing method wherein an ion current isfocused by a magnetic field generated by itself. In this case, anacceleration electrode having a multiplicity of stages may be providedwhose diameter is reduced as it extends downward. Further, when theself-focusing method is used, if an electron current is applied in thedirection opposite to that of an ion current, the amount of theelectrical current will be increased and repulsion between ions will beblocked by electrons (shield effect). This will enhance the focusingeffect.

Then, the ion current passes through magnetic fields 54 and 55 inopposite directions and a slit 56 provided therebetween. The ions aresubjected to a leftward force in the magnetic field 54. As a result,light ions (indicated by the dotted line in FIG. 6(A)) are deflectedfurther to the left than heavy ions (indicated by the thin line in FIG.6(A)) and therefore can not pass through the slit 56. This is similar towhat occurs in the second embodiment. In the present embodiment,however, a more significant effect can be achieved because the ioncurrent is focused.

FIG. 6(C) is a conceptual illustration of the distribution of the ionswhich have passed through the acceleration electrode 52. The ordinaterepresents the density of the ions (ionic strength), and the abscissarepresents the direction of the shorter dimension of a section of theion current. While the ions reflect the distribution of the plasma andhave a shape that resembles Gaussian distribution, light ions are morestrongly focused than heavy ions to be concentrated to a central region.

When the ion current having such distribution passed through themagnetic field 54, light ions move to the left as in the secondembodiment. FIG. 6(D) is a conceptual illustration of the distributionof the ions before they enter the slit. FIG. 6(E) shows the distributionof the ions after they pass through the slit. The slit 56 eliminates thepeak of the light ions located leftward from the ion current. Thus,separation on a mass basis can be carried out on the ion current. Thepresent embodiment is characterized in that the slit provides a moresignificant effect of separation because the light ions are concentratedat a higher degree.

After passing through the slit 56, the ion current is subjected to arightward force in the magnetic field 55 to correct the path thereof.Since the forces applied to the ions in the magnetic fields 54 and 55have opposite directions and the same magnitude, the ion current finallybecomes in parallel with the initial flow.

Thus, an ion current having a linear section can be obtained.

Fourth Embodiment

A fourth embodiment of the present invention will now be described. Thepresent embodiment relates to an apparatus in which an ion dopingapparatus and a laser annealing apparatus utilizing a linear laser beamaccording to the present invention are provided in the same chamber.Specifically, the present embodiment has been conceived considering thefact that the present invention is characterized by a step of doping asubstrate while scanning it with a linear ion current; and a laserannealing process utilizing a linear laser beam according to anotheraspect of the invention needs a similar mechanism to be implemented.

For example, Japanese unexamined patent publication (KOKAI) No.H7-283151 discloses a multi-chamber vacuum processing apparatusincluding an ion doping chamber and a laser annealing chamber. The ideaof integrating an ion doping chamber and a laser annealing chamber hasnot been adopted in conventional ion doping apparatuses which have beenbased on irradiation using an ion current having a planar section at atime and which have sometimes required a substrate to be rotated.

However, according to the present invention wherein an ion dopingapparatus performs doping while moving a substrate with a transportmechanism similar to that of a linear laser annealing apparatus, thereis no need for providing an ion doping chamber and a laser annealingchamber separately, and it is rather advantageous to integrate them fromthe viewpoint of productivity on a mass production basis. Specifically,an arrangement may be made wherein the longitudinal direction of asection of an ion current is in parallel with the longitudinal directionof a section of a laser beam and wherein a substrate is moved betweenthem perpendicularly to the above-mentioned directions. This makes itpossible to perform an ion doping step and a laser annealing stepconsecutively.

The present embodiment will be described with reference to FIGS. 7(A)and 7(B). FIG. 7(A) is a conceptual illustration of a section of anapparatus according to the present embodiment, and FIG. 7(B) is aconceptual illustration of the apparatus of the present embodiment asviewed from above (in the direction in which an ion current isintroduced or in the direction in which a laser beam is introduced).

The ion doping and laser annealing apparatus of the present embodimentcomprises an ion source/accelerator 63, a doping chamber 65, a powersupply device 64, a gas box 69, and an exhaust device 70 like the iondoping apparatuses of other embodiments. In addition to them, however,there is provided a laser device 61 and an optical system 62. Further,there is provided a spare chamber 68. Needless to say, a window 73 isprovided at the doping chamber 65 for introducing a laser beam therein.The window 73 for introducing a laser beam is provided in parallel witha window 72 for introducing an ion current.

A substrate 66 is held by a substrate holder 67 which is moved in thedoping chamber 65 in at least one direction by a transport mechanism 71.A heater or the like may be provided on the substrate holder 67. Thelongitudinal direction of the ion current is a direction perpendicularto the plane of the drawing.

Firth Embodiment

A fifth embodiment of the present invention will now be described. Adevice having an ion forming means and a device having an ionaccelerating means used in the present embodiment have configurations ofthose of the devices shown in FIG. 4.

FIG. 8 is a conceptual illustration of an ion doping apparatus used inthe present embodiment. A dopant gas is ionized by plasma generationelectrodes 82 and 83 to which radio-frequency power is applied by aradio-frequency power supply 81. The resultant ions are extracted by anextraction electrode 84.

The doping apparatus of the present embodiment further includes a means85 for applying a magnetic field to an ion beam. As a result, light ions(ions mainly composed of hydrogen) are deflected significantly. On theother hand, heavy ions (ions including the dopant) are subjected tolittle deflection. In the apparatus of the present embodiment, asuppressor electrode 86 and an acceleration electrode 87 are provided inthe path of the heavy ions to selectively accelerate and radiate such anion beam to a substrate. However, since no acceleration electrode isprovided in the path of the light ions, the light ions are radiated to asubstrate 88 on a stage (not show n) at the energy available whenaccelerated by the extraction electrode 84.

In the present embodiment, the ion beam is radiated to the substrate 88in the form of a curtain like a waterfall. Doping is carried out withthe substrate 88 scanned such that the dopant is evenly delivered to theentire substrate. The dose is controlled by the scanning speed of thesubstrate and the value of the ionic current. The scanning direction atthis time is substantially perpendicular to the plane of the curtainformed by the dopant.

The waterfall of ions formed by the present apparatus has a width of 2meters. This apparatus is used for the purpose of adding phosphorus orboron to a semiconductor material as dopant. The above-described ionsinclude a great amount of H₂+ ions in addition to PH_(y)+ and B₂H_(x)+ions. In the present embodiment, a PH₃ or B₂H₆ gas for semiconductorswas used after diluting it with hydrogen to a density of about 5%.

By forming a magnetic field in a direction which is perpendicular tothis ion current and which includes the plane of the ion curtain, aforce is applied to the ion current in a direction perpendicularthereto. This force is referred to as “Lorentz force”. It will beapparent from the equation of motion Ma=qvB that the acceleration ofions a caused by the above-described magnetic field B is inverselyproportionate to ion mass M and proportionate to ion charge q. Thevelocity component v of the ions after the incidence of the same uponthe magnetic field depends on the ion mass M.

Since most of the ions accelerated have electrical charge at a value of1 in the present embodiment, one can assume that the above-describedacceleration depends only on the ion mass.

The molecular weight of the H₂+ ions, PH_(y)+ ions, and B₂H_(x)+ ionsincluded in the gas used in the present embodiment is about 2, 34, and24 to 26, respectively. When the dependence of the above-describedvelocity component v on the mass is taken into consideration, it will beunderstood that the H₂+ ions are subjected to acceleration 10 to 100times that for the ions including the dopant in the directionperpendicular to the ion current. Thus, the ion current may be separatedon a mass basis by applying a magnetic field to the ion current.

Only the flow of the H₂+ ions could be appropriately changed withoutcausing substantially no change in the direction of the ion currentincluding the dopant by setting the extraction voltage at about 1 to 10kV and applying a magnetic field of about 0.1 to 10 tesla, preferably0.5 to 2 tesla in the direction shown in FIG. 8.

The magnetic field is formed immediately beyond the extractionelectrode. This is because ions can be significantly deflected bydeflecting the ions while the kinetic energy of the ions is still small.H₂+ ions deflected immediately beyond the extraction electrode reach thesubstrate 88 on the stage without passing through the suppressorelectrode 86 and the acceleration electrode 87. This allows the speed ofthe H₂+ ions to be suppressed when they enter the substrate.

The angle of incidence of the H₂+ ions was about 50° when they reachedthe substrate. This angle was sufficient to allow the ions to enter thesubstrate. Meanwhile, the ion current including the dopant passedthrough the suppressor electrode and acceleration electrode and then wasradiated to the substrate without being substantially affected by theabove-described magnetic field. The angle of incidence was substantially90°.

The above-described method of accelerating ions has made it possible toimplant dopant to a desired depth while suppressing the speed of H₂+ions as much as possible. In an equifield, the degree of acceleration ofions increased with a decrease in weight and an increase in electricalcharge. Therefore, unless mass separation is performed on an ioncurrent, lighter ions are implanted at higher speeds. That is, thelighter an ion, the deeper it is implanted in a substrate.

However, according to the present embodiment, the method of the presentembodiment has made it possible to make the speed of the H₂+ ions whichare light ions at the time of incidence upon the substrate substantiallyequal to or lower than the speed of the ions including dopant which areheavy ions at the time of incidence upon the substrate.

Such speed control makes it possible to cause the distribution of theH₂+ ions and the ions including the dopant in the direction of the depthof the substrate to resemble each other. This has made it possible toapply heat generated as a result of the release of the kinetic energy ofthe H₂+ ions directly to the dopant. This heat was used to recoverlattice defects formed as a result of the implantation of the ionsincluding the dopant and to activate the dopant. Further, this heat anda great amount of hydrogen were used to terminate uncombined arms of alattice.

Generally speaking, some corrective action must be taken on damagecaused by doping because it significantly deteriorates thecharacteristics of a semiconductor material. Such damage has beenrecovered by means of annealing means such as applying heat andirradiating it with light. Alternatively, there has been an effectivemeans which adds hydrogen to a portion having such damage and to combinethe hydrogen to lattice defects by means of annealing for the purpose ofterminating the areas having the lattice defects.

Meanwhile, when all ions are caused to enter perpendicularly withoutperforming separation on a mass basis as described above, the speed ofincidence Vα of heavy ions and the speed of incidence Vβ of light ionssatisfies a relationship Vα<<Vβ. Therefore, hydrogen ions which arerelatively light are distributed deeper in a semiconductor film (FIG.10(B)), and relatively heavy ions are distributed in a relativelyshallow region of the film (FIG. 10(A)).

Thus, a center depth d₂ of the former and a center depth d₁ of thelatter satisfies d₁<<d₂. This results in a deviation between thedistribution of the hydrogen ions and the distribution of latticedefects caused by the dopant, which disallows the hydrogen ions to beused for the recovery of the defects effectively.

Meanwhile, when separation of ions on a mass basis was performed and thespeeds of incidence of the ions are made substantially equal using themethod shown in the present embodiment, the depth of penetration of thehydrogen ions (FIG. 10(D)) and the distribution of the dopant (FIG.10(C)) were made close or equal to each other to improve the recovery ofdamage as described above significantly. Such an effect of recoveryincludes the effect of terminating lattice defects provided by thehydrogen ions and a thermal annealing effect as a result of the loss ofenergy of the hydrogen ions and the ions including the dopant in thefilm.

This effect was on the same level of the process (as previouslydescribed) which had been conventionally performed after doping.Although this effect became more significant with an increase in thedensity of the hydrogen ions in plasma, the appropriate density of thehydrogen ions in plasma was 50 to 90% taking throughput intoconsideration.

In scanning a substrate while irradiating it with ions, according to thepresent embodiment, the scanning direction of the substrate wasdetermined such that H₂+ ions would be first implanted in the substrateand then ions including dopant such as PH_(y)+ or B₂H_(x)+ ions would beimplanted. Since H₂+ ions are smaller and lighter than primary atomsthat constitute a semiconductor film, they are implanted into asubstrate without damaging lattices in the semiconductor materialsignificantly, and the kinetic energy that such H₂+ ions lose results inan increase in the temperature of the substrate.

Thereafter, heavy ions including dopant are implanted. The increased,substrate temperature and the hydrogen are used to recover latticedefects produced at this time and to activate the dopant. Thus,annealing and hydrogenation can be performed simultaneously with doping.

Sixth Embodiment

A sixth embodiment of the present invention will now be described. Thepresent embodiment employed completely the same apparatus as that in thefifth embodiment, the only difference being the direction in which asubstrate was scanned. Specifically, when the substrate was scannedwhile irradiating it with ions, the substrate was scanned such that ionsincluding dopant such as PH_(y)+ or B₂H_(x)+ were first implanted intothe substrate and then H₂+ ions were implanted.

Since the heavy ions including dopant are substantially as heavy asprimary atoms that constitute semiconductor film, they have influence onlattices in the semiconductor material which can significantlydeteriorate the characteristics of the semiconductor. Thereafter, theH₂+ ions are implanted, and the kinetic energy that the H₂+ ions loseresults in an increase in the temperature of the substrate. Thistemperature and the supply of hydrogen have a function of recoveringlattice defects and activating the dopant.

The present embodiment had substantially the same level of effectivenessas the fifth embodiment in recovering lattice defects and activatingdopant. The present embodiment indicates that the order of theimplantation of hydrogen ions and ions including dopant into a substratedoes not have any influence on the effects of the present invention.

Seventh Embodiment

A seventh embodiment of the present invention will now be described.FIG. 9 is a conceptual illustration of an ion doping apparatus used inthe present embodiment which is different from the doping apparatusesdescribed in the fifth and sixth embodiments in that it includes a meansfor further applying an electrical field to a region of an ion currentwhich is in a magnetic field. This means also allows mass separation tobe performed on the ion current as the apparatuses in the first andsecond embodiments. The difference is that it can perform massseparation ideally without deflecting the flow of ions including dopantat all. This mass separator is referred to as “E×B separator”.

A dopant gas is ionized by plasma generation electrodes 92 and 93 towhich radio-frequency power is applied by a radio-frequency power supply91. The resultant ions are extracted by an extraction electrode 94.

The ions are further subjected to separation on a mass basis performedby a means 95 for applying a magnetic field to an ion beam and a means96 and, as a result, light ions (ions mainly composed of hydrogen) aredeflected significantly. In the apparatus of the present embodiment, asuppressor electrode 97 and an acceleration electrode 98 are provided inthe path of the heavy ions to selectively accelerate and radiate such anion beam to a substrate. However, since no acceleration electrode isprovided in the path of the light ions, the light ions are radiated to asubstrate 99 on a stage (not shown) at the energy available whenaccelerated by the extraction electrode 94.

In the present embodiment, the ion beam is radiated to the substrate 99again in the form of a curtain like a waterfall. Doping is carried outwith the substrate scanned such that the dopant is evenly delivered tothe entire substrate. The dose is controlled by the scanning speed ofthe substrate and the value of the ionic current. The scanning directionat this time is substantially perpendicular to the plane of the curtainformed by the dopant.

The waterfall of ions formed by the present apparatus has a width of 2meters. This apparatus is used for the purpose of adding phosphorus orboron to a semiconductor material as dopant. The above-described ionsinclude a great amount of H₂+ ions in addition to PH_(y)+ and B₂H_(x)+ions. In the present embodiment, a PH₃ or B₂H₆ gas for semiconductorswas used after diluting it with hydrogen to a density of about 5%.

By forming a magnetic field in a direction which is perpendicular tothis ion current and which includes the plane of the ion curtain, aforce is applied to the ion current in a direction perpendicularthereto. This force is referred to as “Lorentz force”. A lateral force Fapplied to the ion current can be obtained by the equation of motionF=qvB−qE. F may be set at 0 in order not to deflect the ion current.

Since a velocity component v of the ions immediately after the incidenceof the same upon the magnetic field in the direction of the ion currentbefore the incidence upon the magnetic field depends on ion mass M, thevelocity v of the ions including dopant may be substituted in theabove-described equation of motion, and the magnetic field B and theelectrical field E may be adjusted to set the force F equal to 0. Atthis time, since the hydrogen ions has a velocity different from thevelocity v of the ions including dopant, they are subjected to a force Fwhich is not 0. It will be now apparent that the present apparatus canperform separation on a mass basis.

The flow of the H₂+ ions could be appropriately changed by setting theextraction voltage at about 1 to 10 kV and applying a magnetic field ofabout 0.1 to 10 tesla, preferably 0.5 to 2 tesla in the direction shownin FIG. 9.

The magnetic field is formed immediately beyond the extraction electrode94. This is because ions can be significantly deflected by deflectingthe ions while the kinetic energy of the ions is still small. H₂+ ionsdeflected immediately beyond the extraction electrode reach thesubstrate on the stage without passing through the suppressor electrode97 and the acceleration electrode 98. This allows the speed of the H₂+ions to be suppressed when they enter the substrate.

The angle of incidence of the H₂+ ions was about 45° when they reachedthe substrate. This angle was sufficient to allow the ions to enter thesubstrate. Meanwhile, the ion current including the dopant passedthrough the suppressor electrode 97 and acceleration electrode 98 andthen was radiated to the substrate without being substantially affectedby the above-described E×B separator.

The above-described method of accelerating ions provided the same effectas that described in the fifth and sixth embodiments. The presentembodiment is more advantageous than the fifth and sixth embodiments inthat the extraction electrode 94, the suppressor electrode 97, and theacceleration electrode 98 can be made small because the ions includingthe dopant reach the substrate substantially straightly. However, thefifth and sixth embodiments are better from the viewpoint of design andmaintenance because the E×B separator is somewhat complicated instructure. The present embodiment was advantageous in that it did notdepend on the scanning direction of a substrate as in the fifth andsixth embodiments.

The present invention provides an ion doping apparatus capable ofprocessing a large area. Further, the present invention makes itpossible to eliminate the need for annealing and hydrogenation steps, toreduce the processing time of such steps, or to decrease the processingtemperature. The advantages provided by the present invention asdescribed above. Thus, the present invention is advantageous from anindustrial point of view.

While particular embodiments of the present invention have been shownand described, it will be obvious to those skilled in the art thatchanges and modifications may be made without departing from thisinvention in its broader aspects and, therefore, the appended claims areto encompass within their scope all such changes and modifications asfall within the true spirit and scope of this invention.

1. A method for manufacturing a semiconductor device comprising:radiating an ion beam which mainly includes a hydrogen ion to asubstrate, wherein the hydrogen ion beam is elongated in one directionon a surface of the substrate.
 2. A method for manufacturing asemiconductor device according to claim 1, wherein the substrate is aglass substrate.
 3. A method for manufacturing a semiconductor deviceaccording to claim 1, wherein the substrate is moved in a directionperpendicular to the one direction in the radiating step.
 4. A methodfor manufacturing a semiconductor device according to claim 1, wherein adensity of the hydrogen ion is 50 to 90% in a plasma.
 5. A method formanufacturing a semiconductor device according to claim 1, wherein thehydrogen ion is H⁺ or H₂ ⁺ ion.
 6. A method for manufacturing asemiconductor device comprising: obliquely radiating an ion beam whichmainly includes a hydrogen ion to a substrate, wherein the hydrogen ionbeam is elongated in one direction on a surface of the substrate.
 7. Amethod for manufacturing a semiconductor device according to claim 6,wherein the substrate is a glass substrate.
 8. A method formanufacturing a semiconductor device according to claim 6, wherein thesubstrate is moved in a direction perpendicular to the one direction inthe radiating step.
 9. A method for manufacturing a semiconductor deviceaccording to claim 6, wherein a density of the hydrogen ion is 50 to 90%in a plasma.
 10. A method for manufacturing a semiconductor deviceaccording to claim 6, wherein the hydrogen ion is H⁺ or H₂ ⁺ ion.
 11. Amethod for manufacturing a semiconductor device comprising: doping anion beam which mainly includes a hydrogen ion into a semiconductorregion, wherein the hydrogen ion beam is elongated in one direction on asurface of the semiconductor region.
 12. A method for manufacturing asemiconductor device according to claim 11, wherein the semiconductorregion is moved in a direction perpendicular to the one direction in thedoping step.
 13. A method for manufacturing a semiconductor deviceaccording to claim 11, wherein a density of the hydrogen ion is 50 to90% in a plasma.
 14. A method for manufacturing a semiconductor deviceaccording to claim 11, wherein the hydrogen ion is H⁺ or H₂ ⁺ ion.
 15. Amethod for manufacturing a semiconductor device comprising: obliquelydoping an ion beam which mainly includes a hydrogen ion to asemiconductor region, wherein the hydrogen ion beam is elongated in onedirection on a surface of the semiconductor region.
 16. A method formanufacturing a semiconductor device according to claim 15, wherein thesemiconductor region is moved in a direction perpendicular to the onedirection in the doping step.
 17. A method for manufacturing asemiconductor device according to claim 15, wherein a density of thehydrogen ion is 50 to 90% in a plasma.
 18. A method for manufacturing asemiconductor device according to claim 15, wherein the hydrogen ion isH⁺ or H₂ ⁺ ion.